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THE SOLAR NEBULA ON FIRE: A SOLUTION TO THE CARBON DEFICIT IN THE INNER SOLAR SYSTEM
Lee, Jeong-Eun,Bergin, Edwin A.,Nomura, Hideko IOP Publishing 2010 ASTROPHYSICAL JOURNAL LETTERS - Vol.710 No.1
<P>Despite a surface dominated by carbon-based life, the bulk composition of the Earth is dramatically carbon poor when compared to the material available at formation. Bulk carbon deficiency extends into the asteroid belt representing a fossil record of the conditions under which planets are born. The initial steps of planet formation involve the growth of primitive sub-micron silicate and carbon grains in the Solar Nebula. We present a solution wherein primordial carbon grains are preferentially destroyed by oxygen atoms ignited by heating due to stellar accret on at radii <5 AU. This solution can account for the bulk carbon deficiency in the Earth and meteorites, the compositional gradient within the asteroid belt, and for growing evidence for similar carbon deficiency in rocks surrounding other stars.</P>
Tobin, John J.,Bergin, Edwin A.,Hartmann, Lee,Lee, Jeong-Eun,Maret, Sé,bastien,Myers, Phillip C.,Looney, Leslie W.,Chiang, Hsin-Fang,Friesen, Rachel IOP Publishing 2013 The Astrophysical journal Vol.765 No.1
<P>We present a study on the spatial distribution of N2D+ and N2H+ in 13 protostellar systems. Eight of thirteen objects observed with the IRAM 30 m telescope show relative offsets between the peak N2D+ (J = 2 -> 1) and N2H+ (J = 1 -> 0) emission. We highlight the case of L1157 using interferometric observations from the Submillimeter Array and Plateau de Bure Interferometer of the N2D+ (J = 3 -> 2) and N2H+ (J = 1 -> 0) transitions, respectively. Depletion of N2D+ in L1157 is clearly observed inside a radius of similar to 2000 AU (7 '') and the N2H+ emission is resolved into two peaks at radii of similar to 1000 AU (3 ''.5), inside the depletion region of N2D+. Chemical models predict a depletion zone in N2D+ and N2H+ due to destruction of H2D+ at T similar to 20 K and the evaporation of CO off dust grains at the same temperature. However, the abundance offsets of 1000 AU between the two species are not reproduced by chemical models, including a model that follows the infall of the protostellar envelope. The average abundance ratios of N2D+ to N2H+ have been shown to decrease as protostars evolve by Emprechtinger et al., but this is the first time depletion zones of N2D+ have been spatially resolved. We suggest that the difference in depletion zone radii for N2H+ and N2D+ is caused by either the CO evaporation temperature being above 20 K or an H-2 ortho-to-para ratio gradient in the inner envelope.</P>
CO in Protostars (COPS): <i>Herschel</i>-SPIRE Spectroscopy of Embedded Protostars
Yang, Yao-Lun,Green, Joel D.,Evans II, Neal J.,Lee, Jeong-Eun,Jørgensen, Jes K.,Kristensen, Lars E.,Mottram, Joseph C.,Herczeg, Gregory,Karska, Agata,Dionatos, Odysseas,Bergin, Edwin A.,Bouwman, Jeroe American Astronomical Society 2018 The Astrophysical journal Vol.860 No.2
<P>We present full spectral scans from 200 to 670. mu m of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the 'COPS-SPIRE' Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670. mu m, the calculated bolometric luminosities (L-bol) increase by 50%. on average, and the bolometric temperatures (T-bol) decrease by 10%. on average, in comparison with the measurements without Herschel. Fifteen protostars have the same class using Tbol and L-bol/L-smm. We identify rotational transitions of CO lines from J = 4 -> 3to J = 13 -> 12, along with emission lines of (CO)-C-13, HCO+, H2O, and [C I]. The ratios of (CO)-C-12 to (CO)-C-13 indicate that (CO)-C-12 emission remains optically thick for J(up) < 13. We fit up to four components of temperature from the rotational diagram with flexible break points to separate the components. The distribution of rotational temperatures shows a primary population around 100 K with a secondary population at similar to 350 K. We quantify the correlations of each line pair found in our data set and find that the strength of the correlation of CO lines decreases as the difference between J levels between two CO lines increases. The multiple origins of CO emission previously revealed by velocity-resolved profiles are consistent with this smooth distribution if each physical component contributes to a wide range of CO lines with significant overlap in the CO ladder. We investigate the spatial extent of CO emission and find that the morphology is more centrally peaked and less bipolar at high-J lines. We find the CO emission observed with SPIRE related to outflows, which consists of two components, the entrained gas and shocked gas, as revealed by our rotational diagram analysis, as well as the studies with velocity-resolved CO emission.</P>
THE ORIGINAL ENVIRONMENT OF THE SOLAR SYSTEM INFERRED FROM THE OXYGEN ISOTOPE ANOMALIES
Lee, Jeong-Eun,Bergin, Edwin A.,Lyons, James R. The Korean Astronomical Society 2007 Journal of The Korean Astronomical Society Vol.40 No.4
The original environment of the solar system can be inferred by studying the oxygen isotope ratios in the Sun as well as in primitive meteorites and comets. The oxygen isotopic fractionation measured in primitive meteorites is mass-independent, which can be explained by the isotopic-selective photodissociation of CO. The isotopic-selective photodissociation model in a collapsing cloud by Lee et al. (2007) imply the birth of the Sun in a stellar cluster with an enhanced radiation field, which is consistent with the inferred presence of $^{60}Fe$.